1. Field of the Invention
This invention relates to a video signal converter. More specifically, the invention relates to a general purpose scan converter for accepting video input signals and converting them to be displayed on a video monitor having a different scan rate.
2. Description of the Prior Art
Various types of video converters are known in the art. In a typical video converter, a video input signal is provided at a certain scan rate and a processor in the video converter transfers the incoming video data to a converter. The converter provides the information converted into digital form to a monitor to be displayed on the monitor at a different scan rate. Typically the conversion is not in real time because the conversion is performed by first converting all of the red components of the video signal, then converting all of the green components, and then finally converting all the blue components. This type of scan conversion is relatively inexpensive to implement but is very slow.
In another type of video converter called a Time Base Corrector (TBC), the video signal is stored in analog form using charge coupled device (CCD) circuitry. Thus, the entire incoming frame is stored at a real time rate. The output of the CCD is shifted at a different rate, thus providing scan conversion. In another type of video converter, the incoming video data is taken by components (usually only the black and the white components or colored components) at a reduced resolution or reduced color grade. The data is transferred in a mode conventionally referred to as burst mode, which allows the input circuitry to transfer the information through a system data bus to the video circuitry. This type of scan converter has some general purpose applications because it allows transfer to almost any sort of circuitry. It has the disadvantage that software in the scan converter device must know the hardware memory locations. Typically the resolution provided by this system is very poor and relatively small amounts of information can be transferred in real time.
Another type of converter is a video card that can store a video frame at one rate, then, through the use of an expensive multiscan monitor, output the stored video frame at a non-interlaced rate. Another disadvantage is that the video card must continuously be programmed to go between the two scan rates. This converter also does not provide a real time display.
Thus, in the prior art there is no true real time video conversion available that provides a digital output signal for use by a host computer and to be displayed on a video monitor of a different scan rate, i.e., going from interlaced video to non-interlaced. There are no prior art high resolution and high speed video converters available for use in a computer video system which requires digital output data from the converter.